have you tried learning of human anatomy?
Okay, so I also sucked at drawing first, but now I'd like to think I'm a bit better
One of my first full colored character drawings;
And now;
I can suggest you Clip Studio Paint EX
It helped me with its 3D models A LOT when it came to posing etc.
Oh and it was on sale but idk for how long
Related topic;
Also this course thought me a lot about the basics of drawing. Mr. Harris was extremely helpful and he replies DMs as well
If every artist out there would not draw anything because they art lacks fundamentals, all the webcomic sites would look like this
You're doing well in the art part. Now whether you have the guts to start drawing a comic is a whole different thing 
(not saying this in any diminishing way btw, because it could be really hard to start...but you need to just do it)
You have four options:
1. Learn to draw better. Depending on the amount of hard work you put in, taking it to a presentable comic level should take anywhere from a year to five or so years.
You say you have not improved for four years, which to me sounds like you just haven't been studying in a way that works for you? Find different resources, YT channels, online courses, offline art courses, there are countless options really. I know how frustrating it is to try to improve and make seemingly no progress for years, I've been there.
2. Hire an artist. Good if you have lots of money.
3. Draw it anyway. ...but let's face it, there can be only one One (heh), and only this many comics with poor art can be famous. The other 99.9999999% will be just completely overlooked, unfortunately.
4. Give up? I guess this too is some option, not to say I recommend it though.
for the third option I would get rid of any expectation to become popular, I'm speaking from experience here
Honestly, earning money through webcomics is REALLY hard, but you can just earn money with something else and then use this money to hire an artist. I consider doing this myself if I ever get a good job in software development, even though I AM an artist myself. I just think that drawing a comic is too much work.
You can also try to do part of the work yourself so you can pay less. For example, do the storyboard too, so the artist don't have to do it. Or only ask for sketches, and then do the lineart/coloring yourself on top of the sketches. It should be cheaper this way.
My guy I totally understand the way you feel. Your idea is really special to you and you want it to be the best it can possibly be, so you want to find someone or something that can make your vision come to life. I get it because in a lot of ways I am like that, and I think a lot of people who want to make anything creative are like that.
Here’s the thing though, if you really are anything like me you are letting your perfectionism hold you back. You’re happy with your idea now, but who’s to say that in another month or another year you won’t be happy with it again? Who’s to say that you’re not happy with the art in another years time or you find some other flaw you want to fix? The way I see it is that your options for the baseline problem is to hire an artist to draw your idea for you, which is really expensive and forming partnerships can be dicey,or to learn to draw better which is something you seem uncomfortable approaching since it’s something that you’ve tried before but it hasn’t bore fruit like you had hoped. That is completely fine and I understand.
However even if you do do those things I don’t think that they will solve the underlying problem, which is your perfectionism. Personally what I think you really need is to let go of the perfect vision of your comic that you have in your head. I need you to realize that the idea of your story can not and will not ever exist in reality. I know that that can be a bitter pill to swallow, but if you keep trying to translate thoughts onto paper it’s just not going to work out. This is something that I had to learn about myself too. What you really need to learn is to have fun making your project. Even if the art is bad and the writing is crappy if you enjoy the process and you actually create something and have a physical thing in front of you then that is a thousand times more valuable then just having the perfect creation just right in front of you. You believe in your story and you want it to be the best it can be because you want to put your best foot forward and you want everyone in the world to see your vision. I get it, I really do. But if your vision really is as great as you think it is then it won’t matter if the art is bad or the story has some flaws. Comic readers care far more about story then you might think. While it is important to initially attract readers with pretty art and a flashy thumbnail once the story gets into the hundreds of chapter that starts to matter less and less.
To me the thing that seems to be holding you back the most is you. I know because I see a lot of myself in what you’ve been writing, and once I’ve realized that the only thing holding me back is perfectionism and ego I actually started making a project that I’m really happy with. Like, I am happy with the story I’m making right now and I am happy with my art. Both the writing and art are far from perfect and I still plan on improving but I am so close to having that first chapter done and I’m almost ready to share that vision with the rest of the world and my only regret is that I didn’t do it sooner. My only regret is that I hadn’t done it sooner. So I really strongly recommend that you just put your stuff out there, even if you’re not happy with the writing and the art and you try to focus on curbing your perfectionism. We really don’t have as much time as we like to think and it would suck if your vision were to never exist because of perfectionism.
Best way to improve at art is to draw a comic. When I started I could draw talking heads real good, but everything else? Eh. Drawing a comic forced to draw backgrounds, characters from weird angles, etc etc. You know how some (really popular) manga go back and like, re-draw/color stuff for fancy tankonbon editions? Or how some anime, for the bluray version, actually clean up the animation? You can always go back and slowly re-draw (or hire someone else to draw) your comic while pushing forward on the story. A webcomic is inherently a work-in-progress because of the nature of the medium. Just because you drew something once, doesn't mean that's all it will ever be (Just don't get stuck in an endless loop of drawing Chapter 1 Part 1 over and over again... for every two steps forward, you can allow yourself one revision).
Your artwork is better than mine. It doesn't matter if you lack fundamentals. Want to know how much formal art education I have? An intro to art class and a graphic design class. Both high school classes of which I hardly remember. I'm now 32 and have been through college for a completely unrelated path. Where did I really learn? By drawing in my spare time. Looks like that's what you've been doing. And if your art is bad, then mine must be the work of a genius (hint: it's not, and your art isn't bad)
The reason I mentioned One-Punch Man is because the original webcomic's art is not exactly world-class quality art:
If ONE could make it big, then so can anyone. Your story and characters are where the real importance lies.
That's extremely untrue. Art is a difficult skill, and you only get out what you put in. If you want to improve, you have to practice daily. Even then, improvement will be slow, and it may take years to reach a level you're satisfied with for a comic. But you will improve, and the only thing preventing that from coming to pass is your belief that it won't. Growth mindset, bro. 
As for making money off comics, that's extremely difficult, even if the comic is really good. It's important to know that going in, so you won't be disappointed. If you wish to hire an artist, your best bet is putting aside money from your day job.
For People:
There are apps that let you pose your dummies. Clip Studio Paint, for example, is art software that's like Photoshop, and has a shop built in where you can grab free, or paid, 3D dummies for your illustration or comic panels. You can pose them. If you have an iPad, there's Poseit, which is really intuitive, and inexpensive. There's also other apps. I believe Poser even has anime models. You an use these for every single panel. There's no shame in it. In some of these apps you can even adjust the lighting.
I can draw, but the style I'm using for my upcoming comic is one that I believe anyone could replicate even if they picked up a pencil 2 days ago. I still use mannequin apps because it's way easier to visualize things that way, and they're a guide. I know how much to exaggerate a certain feature in comparison to the ones on the mannequin, completely skipping past the need for character turn around sheets that I find horribly boring. 90% of my first episode was done using mannequins.
Many of the top webtoons I come across have extremely obvious, heavy use of mannequins. No one really brings it up nor questions it. They just want the next episode! ^^
For Perspective / Backgrounds
This is a little difficult in terms of tools. There's not really any apps for this, but there are "props". For example, Clip Studio Paint's shop will have free buildings you can adjust how you want, and draw over, or keep as is (but the style difference will be pretty obvious). There might even be trees you can place, I'm not sure, I never looked.
The good news is that perspective, at least far as 1, 2, and 3 point perspective is concerned, is actually really easy to learn! And that's preeeetty much all you points of perspective you see in a lot of online, non-professional comics. Learn how perspective rulers go, learn the vanishing point/s, how lines go to it, etc, and wallah! Without much practice you'll have stuff that looks like buildings.
Organic forms can be a little bit more difficult, like trees and clouds in perspective, but it's still not as complicated as drawing the forms of people. It won't take 5 years of learning, or even 2--possibly just a month or so if you really go at it.
Another alternative, of course, is to learn to draw. This will take much longer, but it's worth it You can still heavily use guides while you're making your comic, but I would suggest learning forms on the side to slowly build on your skill. One day, you won't need the mannequins except for referencing once in a blue moon. I'm using mannequins for my comics and help from a friend for the backgrounds, and on the side I'm starting from scratch on the foundations of art and drawing.
Good luck!
Edit: The story I'm using for my comic is one that's quickly becoming important to me. I know that the art and the execution will still not be perfect, but as my skill grows, I'll be able to reboot the series later on with improved art. There's no rule against rebooting your comic later on. It happens all of the time. I've even seen it a whole bunch of Webtoons, for comics that end up as paid Originals! With the freedom to reboot, there's no excuse beyond our own mind not to start on it. When it comes to things like this we are only trapped as we believe ourselves to be.
There is another variable, some art styles don't fit with certain stories, so, unless there is a deliberate dissonance, the tone will be way harder to convey visually.
There are comics i draw myself, but for one of my projects i hired an artist that could pull of a certain art style that i currently couldn't.
Imma give you some personal experience that you're not gonna like.
First of all, you're not doing so bad on the art department. Is it a bit rough? Maybe, but like many have said, you're already doing better than a lot of people who are already working on comics of their own.
Second, you mentioned you've been doing art for like, 4 years. Sorry to say it but, that's not really that long in artist time. I started drawing 10 years ago, to be fair, i wasn't practicing every day, but semi regularly, it took me like 5 years, just to start to develop a style of my own, and some passable coloring skills. Ten years after picking up a pencil, I'm still not great, but from there to now, I'm miles ahead.
Everyone learns at their own speed, some people can become experts after 2 years, but belive me, that's far from being the rule. And you won't get better until you practice a lot, and practice in a way that works for you.
You don't need to go to art school, most great artists don't, most of what you need you can learn in YouTube and by analyzing other people's art.
Finally, third thing. I've had this idea for a comic for 5 years. I've wanted to start it since then, but i constantly felt like I didn't have the skills to do so till now. Now i kinda regret it. Is the story better for me having waited? Maybe. But i know for sure if I had started then, i would be miles better at art now, and i would have spent my free time getting better at something i love (instead of spending 24/7 reading Homestuck for 3 weeks).
I guess what I'm trying to say is: you don't suck at art, but you're definetly getting ahead of yourself thinking you ""lack the talent"", because that's a myth, no one was yeeted outta the womb with a Monet on each hand. And finally, let yourself suck, sucking is the first step to learn how not to suck.
